<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <form action=""></form>
    <input type="button" value="我是个按钮" onclick="alert('hello')">
    <input type="file">
    <label for="male">男</label> <input id="male" type="radio" name="sex">
    <select>
           <option>北京</option>
           <option selected="selected">上海</option>
       </select>
</body>
</html>